The present application relates to electrical power generation, and more particularly, but not exclusively to techniques to address electric power grid disruptions, faults, and load transients.
During electrical grid disruptions the voltage of the grid can fluctuate rapidly. Under certain conditions, it may be desirable to maintain the grid connection of an engine/generator set (genset) when the grid voltage drops—designated a Low Voltage Ride-Through (LVRT). During a low-voltage event, the generator can lose synchronization with the grid due to the inability of the engine to respond rapidly to the lower power output demand, with the phase angle deviation overshooting due to the now too high engine power output. In some cases, generator damage may be caused by a corresponding pole-slipped induced current when the grid voltage returns and the generator is out of synchronization.
Further, when a load change or momentary electrical fault results in a grid voltage drop, the engine may attempt to compensate by increasing its speed. This increase in speed can result in an unacceptable increase in frequency and/or phase angle deviation of the output voltage. This situation is of particular concern in utility paralleled applications.
Moreover, a line fault event can suppress the voltage to zero and then allow it to return in a period of time that is shorter than a conventional engine and the genset control system can react. This situation can result in the generator phase angle being significantly different than the returning utility voltage phase angle, as the genset control is still reacting to the initial fault, possibly causing damage to the generating equipment. Under certain conditions, a genset with a Spark Ignition (SI) genset engine that mixes fuel and air upstream of the cylinder can be particularly vulnerable. While the quantity of fuel provided can be reduced at the first sign of a load change to ameliorate this result, the fuel charge already in existence can pose a problem. Diesel-fueled genset engines can be similarly vulnerable--even those diesel engines with direct or port fuel injection may perform undesirably during an LVRT event despite the ability to change the fuel charge without having an earlier formed fuel charge present in the intake.
One attempt to address grid fluctuations involves an increase in rotational inertia of the genset by increasing the size/weight of a genset flywheel and/or another rotating mass of the genset. While this approach of increasing rotational inertia may address the problem in part, typically it is not enough to provide desirable performance.
Thus, there remains a need for further contributions in this area of technology.